Deep-blue supercontinnum sources with optimum taper profiles – verification of GAM

Abstract

Abstract:We use an asymmetric 2 m draw-tower photonic crystal fiber taper to demonstrate that the taper profile needs careful optimisation if you want to develop a supercontinuum light source with as much power as possible in the blue edge of the spectrum. In particular we show, that for a given taper length, the downtapering should be as long as possible. We argue how this may be explained by the concept of group-acceleration mismatch (GAM) and we confirm the results using conventional symmetrical short tapers made on a taper station, which have varying downtapering lengths.

Multi-milliwatt mid-infrared supercontinuum generation in a suspended core chalcogenide fiber

“…The fiber dispersion, and in particular the location of the ZDW, is of great importance for the SCG process [35][36][37]. Based on the fiber geometry provided by Perfos and the As 2 Se 3 material refractive index measurements from Amorphous Materials Inc. [38], which were in good agreement with the refractive index of As 38 Se 62 [39], the fiber dispersions of the slow and fast axis were calculated in COMSOL Multiphysics and are shown in Fig.…”

Single-mode pumped high air-fill fraction photonic crystal fiber taper for high-power deep-blue supercontinuum sources

“…A considerable ongoing effort has been devoted to extend the SC into the infrared in nonsilica glasses [2][3][4][5] and into the deep-blue in tapered silica photonic crystal fibers (PCFs) [6][7][8][9][10][11]. Specifically, the deep-blue spectral region below 400 nm is highly desirable for biological applications such as fluorescent microscopy [6], but accessing this region with typical commercial SC sources based on long-pulsed ytterbium fiber-lasers with tens of kilowatt of peak power is only possible with high air-fill fraction PCFs.…”

“…Ultimately, the spectral width is determined, on the long wavelength "red" side, by the maximum extent of the soliton redshift and, on the short wavelength "blue" side, by the GV matching to the solitons. The soliton redshift typically is limited by the increasing material loss at ∼2.3 μm and the blue SC edge can then be predicted by the GV match from this wavelength [7,9].…”

“…Tapering of PCFs with high air-fill fractions has proven an effective way of extending the spectra into the deepblue by shaping the GV landscape [6][7][8][9][10][11]. This facilitates the ideal combination of (1) an initial fiber section to initiate the spectral broadening by MI in the vicinity of the zero-dispersion wavelength (ZDW) with an efficient energy transfer into the visible, and (2) a subsequent fiber section with GV matching to gradually shorter wavelengths.…”

“…This facilitates the ideal combination of (1) an initial fiber section to initiate the spectral broadening by MI in the vicinity of the zero-dispersion wavelength (ZDW) with an efficient energy transfer into the visible, and (2) a subsequent fiber section with GV matching to gradually shorter wavelengths. Previous reports on blue-extended SC generation typically relied on tapered PCFs where the air hole structure is preserved [6][7][8][9][10][11], i.e., with constant hole-to-pitch ratio (d∕Λ) and decreasing hole-to-hole pitch (Λ). However, high air-fill fraction PCFs are inevitably multimode at the pump, which in combination with the large air holes can greatly complicate coupling and interfacing.…”